In recent years, various user interface systems or systems for receiving user input have been proposed. In general, a user interface system is a system by which people interact with a machine (for example, a personal computer (PC)). The user interface system provides a way of input for allowing the user to manipulate a system, and a way of output for allowing the system to indicate the result of the user's manipulation.
It is desired to provide a system for receiving user input which the user can operate in an easy, efficient and enjoyable way.